Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$105.86	10.716%	$117.204	$117.20	$117.20	$117.20
Purchase #2	$100.27	4.785%	$105.0679	$105.07	$105.05	$105.10
Purchase #3	$169.84	12.415%	$190.9256	$190.93	$190.95	$190.90
Purchase #4	$160.59	11.253%	$178.6612	$178.66	$178.65	$178.70
Purchase #5	$107.36	3.654%	$111.2829	$111.28	$111.30	$111.30
Purchase #6	$89.80	3.142%	$92.6215	$92.62	$92.60	$92.60
Purchase #7	$222.25	4.190%	$231.5623	$231.56	$231.55	$231.60
7 purchase totals =	$955.97		$1,027.3254	$1,027.32	$1,027.30	$1,027.40